Outbox Design Pattern

This project shows how to use the Outbox Design Pattern in C#.
It saves messages in the database and sends them safely using RabbitMQ and MassTransit.
It is a reliable, scalable, and maintainable message system.

What is Outbox Pattern?

Outbox Pattern is a way to make sure messages are not lost.
When something happens in the system (like a new user is created),
the message is first saved in the database (the "Outbox table").
Later, a background job reads these messages and sends them to RabbitMQ.
This makes the system reliable and avoids losing messages if something fails.

Key Advantages

• Reliable delivery: Messages are not lost even if the system fails
• Consistency: Database and message queue stay in sync
• Scalable: Consumers and jobs can run independently and scale easily
• Testable and maintainable: Clear separation of responsibilities
• Cloud ready: Can run in Kubernetes or other cloud environments

Features

• Save messages safely with Outbox Pattern
• Send messages with RabbitMQ and MassTransit
• Run background jobs with Quartz
• Use Entity Framework Core for SQL Server
• Map objects with AutoMapper
• Easy to extend with new events
• Jobs and consumers are independent and testable

Technologies

• C# .NET 9
• MassTransit 8.5.2
• RabbitMQ
• Entity Framework Core 9.0.8
• Quartz 3.15.0
• AutoMapper 15.0.1
• Docker

Possible Improvements

In the future, the project can be separated into multiple parts:

• Publisher / API project: To send events to the Outbox table
• Consumer project: To listen to RabbitMQ and process messages
• Jobs project: To run background tasks like sending messages from Outbox to RabbitMQ
• Events project: To store event definitions

This separation can make the system more modular and easier to maintain.
The system can also scale to handle more messages under high load.